The present invention concerns electric utility cross-arms made of lightweight insular materials and having the added qualities of high-strength, ease of construction and repair and durability. More particularly the present invention concerns improvements to cross-arms that permit the quick repair and/or upgrading of electrical service components, while providing high-strength and lightweight characteristics, as well as durability that exceeds that of traditional wood cross-arm systems by two to three times.
Electrical transmission wires require the use of transmission or utility poles that carry the means, typically cross-arms, to permit the electrical transmission wires to be strung from pole to pole so that the electricity can be taken from its point of creation to its point of use. In order to accomplish this, power companies, and others, have used cross-arms of wood, steel, composite materials and concrete to carry power lines. Typically the cross-arms carry electrical insulators often made of glass or other non-conductive material which provide a degree of insulation between the cross-arm and the electrical transmission cables. With prior art cross-arms and insulators, construction methods required that certain insulator be used on certain cross arms for certain situations and conditions. When conditions or situations changed, the cross arms and/or the insulators are required to be changed to accommodate the changes. Often times such changes required that a utility worker climb a utility pole and remove cross arms, insulators and other equipment, using construction techniques that are not easy to do and are particularly not easy to do at the heights that such wires are found.
U.S. Pat. No. 6,027,082 discloses a convertible electric utility cross-arm insulator. The ""082 patent discloses a device and method for converting such cross arms so that they can accommodate a number of different types of utility situations. The ""082 patent further teaches the use of plastic and/or resin cross-arms which provide a lightweight, electrically insulated and durable means of holding electrical transmission wires onto poles and permitting the stringing of transmission wires over great distances. The ""082 patent discloses means to be able to convert a cross-arm from a single line carrier to a double or triple line carrier. The device uses insulating members with threadings, used in association with wire support devices having internal threadings, that permit the support members to be added or removed by screwing or unscrewing the support member from the insulator. In this manner, the cross-arm can be changed, to accommodate different configurations of wires, more quickly than prior art cross-arm members, where the insulator and wire support are more permanently attached to each other. U.S. Pat. No. 6,027,082 is incorporated herein, in its entirety, by reference.
It will be seen, however, that the device disclosed in the ""082 patent has many inherent flaws that make its use, in place of prior art cross-arms, problematic. Such problems, as the need to unscrew or screw parts to replace them, typically at great heights on an utility pole, is an example of the deficiencies of the device of the ""082 patent. Further, in the use of composite materials, typically plastics, such cross arms which are often two part molded products are typically filled, with such products as expanding foam, in order to keep water (which can have deleterious effects on the system) out of the body of the cross-arm. The use of such fillers adds cost to the production of the devices and weight to the cross-arms.
In some cross-arms of the prior art, it has been necessary to use fillers, such as lead filled nuts, as an interference to allow the insulator to be turned and maintained such that the path of the wire on the insulator is perpendicular to the cross-arm. The use of such a system to permit the wires to run perpendicular to the cross-arm causes difficulties in alignment during the setup of cable systems and allows for variability in the settings. Further, there is an added element of increased weight and cost in the use of fillers.
In accordance with the present invention, a lightweight electrical utility cross-arm for quick and easy assembly of an electrical transmission member for carrying electrical wires is provided. The cross-arm member comprises at least one generally vertical opening for receiving at least one insulating member. The cross-arm system further comprises a clip element for holding the insulating member inside of the generally vertical opening in the cross-arm. A wire holding member for insertion onto said insulating member is provided to hold an electrical transmission line in place and in a desirable position, generally perpendicular to the plane of the cross-arm. The insulating member being held in place on the insulating member by the weight of an electrical wire.
In a preferred embodiment the cross-arm member is constructed of a plastic or resin material and is typically created in a molding process. In the construction of the cross-arm member of the preferred embodiment, a single mold is used and is designed so that tongues and grooves are intermittently created in the moldings. The cross-arm is created from two molding pieces (which can be made from the same mold or an identical mold) placed open ends together, such that the tongues and grooves end up opposite each other such that the tongues and grooves fit together to help hold the cross-arm members together. In a preferred embodiment, the cross-arm tongues are created on one half of each mold and the grooves are created on the other half, such that when the two cross-arm pieces (preferably made from the same mold) are placed facing each other, tongues of one molded piece correspond with grooves of the other molded piece, permitting the pieces to fit together and interlock.
The moldings are created such that flanges and beams are created so that a lightweight, honeycomb like structure is created, permitting great strength in the cross-arm. In the preferred embodiment, the cross-arm has a generally diamond shape, adding to the overall strength of the member, and is constructed with generally vertical openings at the top most section of the generally diamond shape and at the two side arms, such that a configuration of one, two or three transmission wires may be made with the cross-arm member.
In a preferred embodiment of the present invention insulating rods, having a tongue or tab at one end, such that it can fit into a groove or slot in the cross-arm, are provided. In a preferred embodiment, the tab is specifically designed to assure correct wire-groove rotation and orientation. The insulating rods further comprise notches near their bottom ends, such that a cotter-type spring pin, xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d style clip, may be placed onto the notches to keep the insulating rod in place. In a preferred embodiment, the notches are generally horizontal and the clip are typically xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d shaped clip. The cross-arm of the present invention defines a slot; located adjacent to the generally vertical cylindrical opening, such that when insulating rod is placed into the generally vertical opening, and the tongue or tab of the insulating member is fitted into the groove or slot in the cross-arm at the base of the generally vertical opening, the cotter-type spring pin may be inserted into the slot in the cross-arm, through the notches in the insulating member, such that the insulating rod is locked into the cross-arm until it is desired that it be removed by pulling the xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d clip out. In this way, repair or replacement of component parts of a cross-arm member system, such as insulating rods or wire supports, requires only a minimum of time atop an utility pole and little or no skill to lift the support off of the insulating rod, remove the xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d clip, and replace the rod and support. Addition of a rod, pin and support to a cross-arm member to accommodate the addition of a new electrical wire, is also facilitated.
The xe2x80x9cCxe2x80x9d or xe2x80x9cUxe2x80x9d clip of the preferred embodiment of the present invention is typically constructed so that it comprises a generally flat portion having two elongated tines emerging therefrom. In a preferred embodiment the tines are designed such that the spring-clip, when engaged, is always under tension so as to prevent its becoming disengaged. In a preferred embodiment, the clip comprises a series of undulations that permit it to be better locked into place until removal is desired.
The slot or groove within the generally vertical opening, in a preferred embodiment, is constructed such that it ramps downwardly from the center of the slot to the edge, near the outside wall of the cross-arm body proper (forming a generally inverted V-shaped). The outside wall of the cross-arm is, further, provided with a weep-hole opening intersecting the slot or groove. In this manner, any water entering the cross-arm through the generally vertical opening, or any other adjacent openings, (by means of precipitation or the like) can be naturally eliminated. The slot or groove thereby performs the dual function of permitting the mating of the insulating rods with the cross-arm and as a means to drain any fluids from within the cross-arm body.
In a preferred embodiment of the present invention, insulating wire holders having a simple cylindrical opening created through the center bottom are used. The insulating wire holders are simply slid onto the insulating members to make a simple friction fit, generally held together by the weight of the electrical transmission cable placed thereon.